Gun for spraying metal



Feb. 13, 1940. Cj HOLMES A.2,190,153

GUN FDR SPRAYING METAL Filed April 13, 1937 2 sheets-sheet 1 A INVENTOR(UHT/.5 HOLMES ATTORNEYS.

Feb. 13, 1940. c. HoLMEs I 2,190,153

GUN FOR SPRAYING METAL Filed April 1s, 19374 2 sheets-sheet 2 E917 H46'vINV ENT OR. C we T/ s HOLMES ATTORNEYS Patented Feb'. 1 3, 1940 GUN FOBSPRAYING METAL Curtis Holmes, Chattanooga, Tenn., acaignor to TaywalCorporation, Chattanooga, Tenn., a corporation of Tennessee ApplicationApril 13, 1937, Serial No. 136,644

4 claims 'Ihis invention relates to a. gun for spraying metal, and moreespecially to a gun of the nature of a pistol having a crucible or wellfor receiving and discharging'the metal stock, and means for 5 meltingand spraying the metal. As in the prior application of Carl G.Neidhardt, Serial No. 106,138, flied October 17, 1936, owned by theasslgnee hereof the present gun has a heating head on the muzzle end ofits barrel, the headcontain- 1 ing anfelectrical resistance heatingelement in operative association with the crucible or well, the latterbeing arranged vertically and with its outlet at the lower side of thehead. Spraying uid is supplied by means of a tube having acrescent-shaped orifice directed across the discharge outlet of thecrucible or well. Current` is supplied through a hollow frame or barrel.portion aligned with the head, and there is a breech cap for supportingone end of a suitably insulated electric service cord. A downwardlyprojecting handle is secured to the underside of the hollow frame orbarrel member mentioned, and air is supplied to the tube through asuitable \valv located in the handle. i

One diiliculty encountered in the use of metalspraying guns, arranged asabove described, arose from the practical necessity of making the barrelportions of the gun (the head and/or frame) out of very light metal,such as aluminum. Such has an enormous advantage in reducing fatigue onthe part of the operator, it being manifest thatiftheguncanbemadeaslightaspossiblethe operator will be able to controlit and direct it better over long periods of time. However, aluminum hasa relatively low melting point, as compared to bronze and other heaviermetals that might be used for the head and/or other gun and barrelparts. Heretofore it was considered necessary to limit the heatingcapacity of the heating element in order notv to damage the gun bymelting or partially melting the metal of the head. This necessarilylimltedthe operating period, i. e. the time. during .which metals ofrelatively high melting point could be continuously sprayed. I

With the above in view. an object oi the present invention includes theprovision of an electrically heated gun for spraying metal, which can besafely operated for continuous spraying.

Another object is to provide a gun for spraying metal, wherein, duringnon-operating periods, the effective temperature of the gun may besafely maintained suiciently high to melt or nearly melt the metal to'besprayed, and where- 66 in sumcient heat to enable7 continuous spraying(c1. en -12.2)

may be applied without substantial loss of time (as in waiting for thegun to heat up) whenever it is desired to use the gun for spraying.Another object is to provide an improved electrical vheating element forguns adapted to spray metal. 5

Another object is to provide a gun which will automatically superheatwhenever an attempt is made to use it for spraying. A specific object isto provide an automatic control for superheating in connection withsupplying spraying fluid, l0 such as air, to the spraying nozzle of thegun.

Another object is to provide an alarm device which will inform theoperator when a predetermined temperature change has taken place, andspecically to enable the operator to know 15 definitely when it is safeto lay the gun aside or hang it up, for use later. n

Another object is to provide a cooling system for a gun of the typeabove outlined, whereby air is automatically passed through certain por-20 tions of -the gun, during its operation to spray metal.

Another object is to provide a simple and convenient means fordetachably securinga heating element in place in operative associationwith the 2.5 crucible or receptacle for metal to be sprayed.

Another object is to provide for facilitating the assembly anddisassembly of guns of the type shown.

Another object is to provide an improved and 30 simpliiled means foradjusting and locating a tube or jet for spraying fluid such as air,relative to the discharge outlet for the metal to be sprayed. Otherobjects include the provision of a more effective means for preventingoverheating of 35 certain parts of the gun by conduction of heat fromone part to another.

Other objects and features of the invention will become apparent fromthe following description,

relating to the accompanying drawings, which 40 show the preferredforms. The essential characteristics are summarized in the claims.

Referring to the drawings, Fig. l is a side elevation, showing theimproved gun in one form; Fig. 2 is a central, longitudinal, sectionalview, L45 ofsaid gun; Fig. 3 is a view similar to Fig. 2

' showing a modified construction; Fl'gs. 4 to 6 are transverse,sectional views taken as indicated by the lines 4 4, 5-5 and 6 6,respectively, on Fig. 2; and Figs 'I and 8 are diagrammatic views 50showing different electrical hook-ups.

The barrel parts of the gun, as shown in Figs. 1 to 3, comprise a hollowbody member I (heremarrer canes a frame) which is generuy cylindrical inform, and adapted to be made of cast u of slots Ia (e. g. saw cuts) inboth sides which assist in keeping the frame cool. A heating elementhousing or head 2 (also preferably cast aluminum) is attached to theframe in alignment therewith but preferably spaced from it to reduceconductivity of heat to the frame. A

. breech closure 3 for the frame is located opposite tically disposedtapered bore I0, near its outer end, which bore serves as a crucible -orwell for the metal to be melted and sprayed. The lower end of the wellhas a restricted discharge tip Il shown as a separate piece inserted inthe lower end of the bore I0. The tip is preferably Monel metal and maybepeened or screwed into place.

2n, The aluminum of the casting 2 may be spun or `the heating elementI3.

headed over the top rim of the tip to hold it.

Directly behind the bore Ii) the head 2 is bored The element will belater described more in detail. Beneath the pocket I2, and parallel toit, is a through bore I4, which receives the outer end portion of a tubeI5 for spraying-fluid, such as air or other gas, the tube being spacedfrom the walls of the bore I4, and having a generally crescent-shapeddischarge orifice I6 properly related to the discharge orifice of themetal discharge tip II, so as to spray metal therefrom in theform of atrough. Other shapes for the spray nozzle may, of course, 'be used.

The tube I5 may be made of relatively hard non-corrosive metal, whichwill not 'warp under intense heat; Monel metal being preferred :inseamless, thin walledI tube form. The tube may be located centrally ofthe bore I4 by means of one or more discs II, say `of insulationmaterial such as-lava, each centrally apertured to receive andsubstantially fit the-tube and having its outer marginal portions cutaway, as at I8. (see Fig. 5) so that circumferentially spaced portionsofthe disc contact with the bore and main--v tain the tube centered in thebore, while the cut-away portions I8 providefree passage for air fromonev end of the .bore I4 to the other. Additional meansfor locating-theextreme end of or cored as at I2 to form a pocket for receivingr? f.

the tube I5 may comprise a suitable arrangement'of adjusting screws; forexample, two horizontally extending screws 20, one on'each side of thebody bore, and a bottom screw 2| which bears 'upwardly against the freeportion of the tube near its end. 'I'he screws may tightly fit theirthreaded.openings, for locking effect when adjusted to position' thevcrescent-shaped discharge orifice of the tube properly relative to thedischarge orifice o'f the tip II. e

The purpose of insulating the tube I5 from the heat of the metal body 2is partly to reduce the character. When the gun is operated, the fluidvprojected from the crescent-shaped nozalehas va.

` i25,199,153 laluminum or other light metal. I This has a seriesVenturi action on the air adjacent the nozzle and surrounding the tubeI5 and draws Vair through the bore I4 and passages I8 from the interiorof the frame I, thus not only cooling the interior of -the frame, butalso keeping the wall of the tube comparatively cool.

As shown in Fig. 2, the rearward end of the head 2 is secured to thebarrel lmember I, by means of three rods 25 which are preferablythreaded for their entire length, partly to pro- 'l0 vide heat radiatingns on the rods. The outer threaded ends 26 of the rods are tightlyscrewed into appropriate threaded openings on the rear face of the head2.- The Shanks of the rods radially abut notches in inwardly extendingear portions 2l, formed on the inside of the fr ame l' intermediately ofits ends, thus locking the head against turning with reference to theframe by substantially a minimum of heat-conducting contact-betweenparts of the head and the frame, near the head. The rearward threadedends of the rods 25 may slide through parallel openings in inwardlyextending ears 29 ofthe frame, adjacent the breech closure; the saidends extending outwardly at therear face .of the frame I, for supportingthe breech closure 3.

In order to provide for adjustably spacing the head from the Vhollowframe I as indicated at 30, Figs. 1 and 2, the rods carry collars 3l,tightly threaded on the rods and adapted outwardly to abut the ears 29.The space at 3l) is preferably alf" wide. The collars are mounted on therods before the rods are inserted into the outer end of the frame I, andthe rods are slightly sprung inwardly in order to move the collars pastthe ears 21. The collars are drawn tightly against the ears 29 when thebreech closure 3 is mounted on the frame.

The breech closure or cord support 3 may be secured in spaced relationto the rear face of the frame I, providing an air gap 28, as by washers32, "interposed between the closure and frame ears 29. The closure isappropriately apertured slid- .ably to receive the rear threaded ends ofthe rods, and is clamped in place as by nuts 34, one'for each rod. Theelectric cord 5 extends through a central boss 35 on the cap 3, and maybe supported by theusual coiled wire ferrule embracing thel cord andmounted in the breech closure.

Referring again to the heating element I3, this preferably comprises aporcelain or lava spool 40, having a helical arrangement 'lof grooves42, to retain coils of resistance lwire surrounding the spool. There maybe two sets of coils, 43 and 44, each of different size wire andconnected, as end to end, so that they may beoperated simultaneously inseries. If the portion 43 is of lower resistance than the portion 44,and current is supplied to both (in series) for maintaining heat duringperiods of non-use of the gun, only the higher resistance wire (portion44) will attain glowing heat. If current is supplied only to the portion42 then this will attain a much higher temperature than when bothreceive current, in series. vThis illustrates one arrangement ofobtaining storage and superheat, the control for which will be laterdescribed.

The spool 40' may be mounted in the bore I2 by sliding it into place,and may be retained by a lava or porcelain disc 45, the central portionoi' which abuts the end of the spool. The rim of the disc is notched at45, adjacent. each of the rods 25, so that the disc is held in placeagainst `turning and against lateral displacement by the rods. The rodsthus maintain uniform air passages between the rim of the disc and thewall of the frame I. 'Ihe disc may be heldin place against movementlongitudinally of the frame by a snap-ring 41 of the spring wire whichengages the threads of the rods when expanded in contact with the disc.The disc carries suitable binding posts 43a, 43h, and 43e, for theconductor leads 49a, 49h and 43e which pass inside the spool and areconnected tc the different portions of the coil as shown on Fig. 2.

Referring now to the handle attachment, this may comprise in part, aplate 53, which is secured as by a pair of screws 5I, entering slots 52,in the plate, the slots extending lengthwise of the frame I, and thescrews being threaded into the under side of the frame. The tube I5 hasa downwardly extending portion IIa extending through an enlarged opening53 in the frame, said extension being secured as by threading at 54 intosealed relationship to a valve chamber 55, located in the handle. Theplate 53 is rigidly attached to the handle (as by means to be describedlater) so that when the screws 5I are slightly loosened and theplateshifted longitudinally of the gun,

' the tube I5 and handle may be moved bodily ina manner to adjust theposition of the discharge orice of the tube closer to or fartherl awayfrom the axis of the discharge 'tip I I, there-'f by to vary the natureoi' the spray. For instance,x

when the tube is relatively withdrawn, a wider spray is "effected thanwhen the. air discharges closer to the tip.

A suitable means for reducing conductivity of heat from the frame I tothe metal handle may comprise (see Figs. 2 and 6), a plurality ofspaced, superposed metal plates 33, the spaces being maintained by rings5I, through which attaching bolts 52 extend, from a block or plate 54 ofinsulation material upwardly through holes in the plate 5I! to which theends of the bolts may be secured as by nuts 63. The block 54 is attachedto the upper face of the handle by separate screws 36 which enter theblock from its top side, and being threaded into the top fac of thehandle. v

The valve chamber 55, above mentioned, communicates with a conical port`58, leading to an air inlet 69, into which a tube or sleeve 10, adapt- Yed for attachment to a flexible air-hose, is

threaded.

'I'he air control valve may comprise a ball 1I, arranged to seat in theport 53, being pressed thereagainst as by a coil spring 12, one end ofwhich seats against a counterbore in the tube 10. An operating stem 13for the ball extends through asuitable borein the front face of thehandle, to ahead 13', having a sealing gasket 14 beneath it, whichsurrounds the stern and seals the'opening for the stem when the valve isfully opened. A trigger device 15 suitably pivoted on the handle, servesto.release the valve and permit the owof air intothe tube I5 through thetransverse tube portion I5a.

For controlling the heating element automatically so that diilerentheating efIects are obtained during idle and active periods ofthe gun,Fig. 2 shows a device which is responsive to a prede termined nuidpressure in the air tube between the control valve and huid-dischargeorice I6. The device acts to turn on more heat whenever the gun is usedand includes a rdiaphragm housing 30 at the rear end of a -branchportion I5b of the air tube. The diaphragm 3I may be made of springmetal and may normally occupy a iorwardly sprung position such asillustrated in back pressure of air in the tube I5 when air is admittedto the tube as by opening the control valve. This closes an electricalcircuit including electrical contact members 32 and 33 at the back ofthe diaphragm, the contacts being electrically bridged directly by thediaphragm or suitable conductor means-'operated byfit, as desired.

While 'the electrical connections may be Vnously arranged depending onthe manner in w ch the element I3 is wired, the connections in casev ofthe large and small resistance wire 43-44, to be used in series, maybeas follows:

Service wire 35 of the cord 5 is connected, as by the branch 86, to thediaphragm housing contact 32 and also, as by branch 31, with the post43h on the element-retaining disc 45. Another service wire 38 of thecord extends as at 33 to the binding post 43a of saidd isc. 'Since thetwo binding posts mentioned are connected respectively to the effectiveends of the coil 4344, plugging in of the cord onto a' service linepasses current through both portions of the coil. This heats up theportion 44 and the resistance of the wire is of such nature (compositionand/or length) that the coil now draws in the neighborhood of 200 watts,or suilicient to maintain the head 2 at melting temperature of the metalto be sprayed, but insuicient to damage the alumi-- num head of the gun.

The contact 33 of the diaphragm-operated switch is connected as by aline 33 to the post 48e on the disc 45 which, as above mentioned, isconnected (by line 43e) to the inner end of the outer portion 43 of theheating coil. By this arrangement, as soon as the back pressure of airin the tube I5 closes the switch 3-82-33, the coil portion 44 is shortcircuited and rendered ineffective. Thereafter, so long as air pressure,suilcient to spray metal is maintained in the tube I5, appreciablecurrent flow is through the coil portion 43 only. The coil is preferablyso proportioned (and/or composed) that it draws in the neighborhood of500 watts to maintain the condition of superheat, and if it were not forthe fact that airis now being supplied through the discharge nozzle I6,drawing air through the bore I4.and also withdrawing considerable heatfrom the head by removing melted metal from the well III, the heat ofthe element would be suilicient to melt the aluminum head. However,absolutely no damage results from such super'. heating while the gun isoperating to spray metal. As soon as the operator stops supplying air,as by releasing the trigger 15, the diaphragm 3I then springs away fromthe contacts 32 and 33, the line wire coil portion 44 is replaced in thecircuit, and the added resistance immediately decreases the amount ofheat supplied by the heating element. It is then safe to hang up the gunor lay it aside.

' coil may be in parallel, and, in that event, the

diaphragm operated switch would cut one of the coil portions entirelyout of `the circuit to reduce heating of the head. In other vwords thedla- 'I'he diaphragm 3I, when it snaps forwardly to break the circuit35-33,

' is used for spraying metal.

' tion obtains in the gun. For instance, a suitable As a suitable signalor tell-tale, a light bulb may be mounted inside the frame I and so con#nected into the electrical circuit that it informs the operator when apredetermined heat condilow-wattage bulb 84 may occupyI a socket 95mounted on the closure member 3 and having its effective terminalselectrically connected with the binding posts of the contact members 82and 83, thus causing the light to operate in parallel circuitarrangement with respect to the heating element portion 44. Thus, thelight is by-passed in the circuit when the switch 8|, 82, 83 is closedand the gun operates at superheat In other words, the light goes outduring normal operating periods of the gun, and whenever the switchbecomes effective to reestablish low heat, then the light shines throughthe window openings provided by the side slitsIa in the frame, to remindthe operator that the gun is still plugged in on the service line andalso to inform him that it is then safe to hang it up as by the loop Ibawaiting arrangement of work, etc. No time is lost (waiting for heat)when the operator is ready toy resume spraying.

It may be noted that any appropriate audible signal could be usedinstead of the visible one described, it being contemplated that, forinstance, the switch may be of the type which snaps or clicks to on andoff" positions as a suitable tell-tale of the heat setting of the gun.

The electrical connections above described are shown more simply in thediagram, Fig. '7, which will be self-explanatory, in view ofthe above,and reference characters on the diagram.

The signal might be connected in parallel with either heating elementportion when the elementsv operate in parallel as above mentioned (oneportion cut out of circuit to reduce heating, so that, for instance,4the light goes on when the gun is operating to superheat, and goes out,during storage-heating periods).

Fig. 8 shows a modification of electrical hook--A up, which may be used,and in this, one main line,

- say 85 is connected at an intermediate point with the heating coil,having portions 43x and 44x. One end of this coil, e. g. extremity of43m, is permanently connected as bythe branch 88' of the main line 88,to such main line. Thus, when the plug of cord 5 is connected with aservice circuitv and switch member 8|:I: is in the position in whichshown on the diagram, only the -portion 43a: of the coil becomes heated;therelmainder of the coil 44:1: being unsupplied with degree. Obviously,other arrangements of electrc'al circuits and switches can be arrangedto effect the essential purposes above described, as well known' toelectrical engineers.

3, only so much of this' will be specically described as diners/from theshowing of Fig. 2. In this arrangement, means are provided forcontrolling the heating element either in connection with the air supplyvalve 1| or independently thereof, as by a separate trigger or switch,but in any event so that superheat control is independent of airpressure. Another difference resides in the manner in which the mainbarrel parts, I, 2 and 3, are assembled and held together as by two ormore attaching stud assemblies (three preferred), one only of which isshown in detail and described below.

-Atthe upper portion of the barrel in Fig. 3,

|00 designates a relatively short stud section having its forwardshouldered end screwed into the head 2 as at |0I. The shoulder, providedby an enlargement |02, seats in one ofthe edge recesses 46 of the disc45. These stud sections |00 may be of stainless steel and as shownthereare heat radiating fln eilects on the shank portions. The frame Ihas inwardly extending ears at |04, which are countersunk on theirforward sides to receive fixed enlargements |08 on the stud sections|00. The threaded rearward extensions IIII of the stud sections |00extend through the ears |04 for engagement by internally threaded studs|09, the bshanks of which may be of the same diameter throughout theirlength; or which may be made as shown, with enlarged threaded outer ends|08 secured to the relatively reduced shanks as by threads and/orsolder, or by welding. Head effects ||0 on the studs |08 (heads may beseparate nuts) clamp the end closure 3 to the frame, or against spacemaintaining washers 32, when the studs are-tightened onto the rearwardlyprojecting ends |01 of the stud sec-V tions |00. The fixed shoulders |00maintain the proper space at 30 between the head 2 and the frame I, andthe studs |00 cooperate to clamp all of the main parts of the barreltogether. In the event separate nuts replace the heads ||0, then, theouter ends (e.v g. sleeves |08) are seated against the forward faces ofthe ears |04 (or against spacers or lockwashers for same effect),

`before the end closure 3 is applied, thus making a rigid sub-assemblyof the head 2 and frame which is independent of the end closure member.

Referring to the control switch, a pair of spring .contact members IIBand IIB may be mounted on a suitable insulation block assemblysupported, as by a bracket II8, held in place by one or more of the nuts63, previously described. The ends of the spring contact members extendloosely into a cavity |20. formed in the top oi'. the handle. As shown.the forward contact IIS, is arranged to be pressed against itscooperating contact by the air-control trigger 'I5, through the agencyof a pin |23 the head of which is normally maintained Vagainst thetrigger, as by a light compression spring |24, bearing against thehandle. switch could, ofcourse, have an actuator which is independent ofthe aircontrol trigger.

The upper ends of the contacts ||5 and lI I6 are suitably connected withthe binding posts 48a, 48h or 48c (the latter two, as shown) in suchmanner that when the contacts are brought together the heating elementis conditioned for TheA superheating as by any of the electricalarrangements already described. It will be noted that superheatingoccurs only after the airvalve has been opened, and the coolingoperations-tending v Referring to the `Arrangement shown in Fig.tomaintain a safetemperature, notwithstanding the higher application ofheat, has become eiective.

No signal is shown in connection with Fig.` 3, but it will be understoodthat a visible or audible signal may be arranged in this form, in any ofthe ways already referred to. 'Ihe necessary modication of switches toenable simultaneous use o! two coil portions for superheating i. e.boosting eect according to Fig. 8, will be obvious to anyone skilled' inelectrical construction.

I claim:

1. In a gun for' spraying metal having an electric heating head andheating element therein for melting the metal to be sprayed, a hollowbody section through which conductors pass to.

the heating element, inwardly extending ears on said section, rodsattached to the head and extending past the ears, supported thereby, anelectric cord support positioned to close the end of the hollow sectionopposite the head and attaching members passing from said support intothe hollow section and detachably asso- 'ciated with the extendedportions of the rods.

a disc capable of being slid into and out oi' the passage with the tube,said disc being apertured to receive the tube and having edges whichcontact with the walls of the passage to support the tube in a deniteposition, other portions of the disc being notched to provide openingsspaced. circumferentially of the Adisc to permit flow of air through thepassage externally of the tube for cooling.

3. In a gun for spraying metal, an electric heating element disposed ina hollow head member having threaded positioning rods projectingtherefrom adapted to attach the head to a supporting body, a discarranged to hold the element in the hollow head, said disc havingpassages therein for electrical conductors adapted to extend from thesupport to the element, and a spring retainer adapted to engage thethreads of the rods to hold the disc in place. i

4. In a gun for spraying metal, having an n electric heating elementarranged to melt the metal, a hollow head for the element, a hollow bodysection aligned with the head, a plurality oi attaching rods extendingfrom the head and heating element, said attaching means being de`tachably secured to the ends of the rods.

CURTIS HOLMm.

